1. Field of the Invention
The present invention relates to a device for applying a crumbleable solid product, presented in the form of a stick and mounted so that it can slide in a case. This solid product is, for example, a stick of coloured or colourless lipstick, of foundation, of eye shadow, of blusher or alternatively a skin-care stick for the selective treatment of certain afflicted parts of the skin or lips. More specifically, the invention is aimed at an applicator device which is particularly well-suited to sticks that contain, in particular, water or volatile ingredients such as volatile oils containing silicone or hydrocarbons.
2. Description of the Related Art
Typical lipstick applicators comprise a tubular case in which a stick-holding cup capable of sliding axially in the case is mounted, the base of the stick of crumbleable solid product being fitted into the cup. In the conventional way, such a lipstick applicator further comprises drive means, for example a rotating thumbwheel, via which the user can slide the cup in the case to make the stick protrude or to retract it as desired. After the applicator has been used, it is closed with a cap held fixed on the case.
When the crumbleable solid product contains, among other ingredients, volatile compounds such as alcohol or volatile oils containing hydrocarbons or silicones, or alternatively water, it is desirable to limit or even prevent the evaporation of the volatile compounds of the stick of product in order to conserve the product's properties. Furthermore, some ingredients of the solid product may be sensitive to oxygen and their degradation may detract from the properties of the product. It is therefore desirable to reduce, or even to prevent, contact between the stick of product and the surrounding air. Therefore, it is necessary to reduce the volume of air in contact with the stick of product in the case when the applicator is closed and to keep this reduced volume of air constantly sealed so as to prevent renewal of air in the reduced volume.
To limit the contact between the stick of product and the surrounding air, U.S. Pat. No. 5,533,823 describes an applicator as previously defined equipped with a sealing sleeve tube in the form of bellows, in a closed end of the cap. The free end of the bellows defines a sealing surface intended to cover the open end of the case when the applicator is closed by the cap held fixed on the case. However, the bellows allows only an axial movement of compressing or expanding the sleeve tube and the sealing surface can move only in this axial direction. To close the open end of the case in a sealed manner, the bellows has to be compressed uniformly over its entire periphery, and this means that the free end of the bellows has to rest on the open end of the case. In order to uniformly compress the bellows, the cap has to be correctly positioned on the case when the latter is closed by the cap. When the user shuts the applicator quickly, the cap is not necessarily correctly positioned on the case and the free end of the bellows does not rest over the entire open end of the case. The bellows therefore does not compress correctly and sealing is not satisfactorily ensured over the entire periphery of the open end of the case.
Furthermore, commonly used cases do not necessarily have an opening with an edge that defines a plane perpendicular to the axis of the case. For example, the edges of cases may have undulations or define a plane which is inclined with respect to the axis of the case. The bellows described in U.S. Pat. No. 5,533,823 does not compress in such a way that its free end follows these particular profiles. Therefore, it is unsuited to the sealed closure of cases which have these particular profiles. In this case, contact between the free end of the bellows and the open end of the case is not sealed against the air and against the volatile products which may be present in the stick of product.
U.S. Pat. No. 4,168,128 teaches an applicator for a liquid product, comprising a sealing system in the form of a piece of foam placed in the cap so as to prevent leaks of product, when the applicator is closed by the cap. This applicator is of the type in which application is by transfer using a roller that rotates in a casing, the roller being pressed onto the surface to be treated. This arrangement requires fitting of the foam and shaping "in situ", which is disadvantageous from the industrial point of view and difficult to master from the technical point of view.